Transcript of "Fingerprints"

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Chapter 14 Fingerprints

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History <ul><li>Alphonse Bertillion </li></ul><ul><ul><li>French police expert </li></ul></ul><ul><ul><li>First systematic attempt at personal identification was </li></ul></ul><ul><li>Bertillion system </li></ul><ul><ul><li>Relied on a detailed description of the subject </li></ul></ul><ul><ul><li>Combined with full length and profile photographs </li></ul></ul><ul><ul><li>System of precise body measurements called anthropometry </li></ul></ul>FINGERPRINTS

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History <ul><li>Dr Juan Vucetich </li></ul><ul><ul><li>Devised a classification system </li></ul></ul><ul><ul><li>Still used in most spanish-speaking countries </li></ul></ul><ul><li>Sir Edward Henry: system used in most English-speaking countries. </li></ul><ul><li>Will West and William West case </li></ul><ul><ul><li>1903 </li></ul></ul><ul><ul><li>Bertillion system could not distinguish between men </li></ul></ul><ul><ul><li>Fingerprinting that clearly distinguished them </li></ul></ul>FINGERPRINTS

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History <ul><li>Fingerprinting used by the New York city civil service commission in 1901 </li></ul><ul><li>Training of American police by Scotland yard representatives at the 1904 world’s fair </li></ul>FINGERPRINTS

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Principle One <ul><li>Mathematical probability for existence of two identical fingerprint patterns in the world’s population = almost zero </li></ul><ul><li>Millions upon millions of individuals who have had their prints classified </li></ul><ul><ul><li>No two fingerprints have been found to be identical </li></ul></ul>FINGERPRINTS

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Principle One <ul><li>Individuality of fingerprint not determined by its general shape or pattern </li></ul><ul><li>Careful study of its ridge characteristics, known as minutiae. </li></ul><ul><ul><li>Identity, number, and relative location </li></ul></ul><ul><ul><li>Individuality to a fingerprint. </li></ul></ul><ul><li>As many as 150 minutiae on the average finger </li></ul>FINGERPRINTS

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Principle One <ul><li>Three year study </li></ul><ul><ul><li>“ No valid basis exists for requiring a predetermined minimum number of friction ridge characters which must be present in two impressions in order to establish positive identification” </li></ul></ul><ul><li>Judicial proceeding </li></ul><ul><ul><li>Expert must demonstrate a point-by-point comparison </li></ul></ul><ul><ul><li>To prove the identity of an individual </li></ul></ul>FINGERPRINTS

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Fingerprint Comparison Figure 14–2 A fingerprint exhibit illustrating the matching ridge characteristics between the crime-scene print and an inked impression of one of the suspect’s fingers. Courtesy New Jersey State Police.

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Principal Two <ul><li>Epidermis </li></ul><ul><ul><li>Outer layer of the skin </li></ul></ul><ul><li>Dermis </li></ul><ul><ul><li>Inner layer of the skin </li></ul></ul><ul><li>Dermal papillae </li></ul><ul><ul><li>Layer of cells between the epidermis and dermis </li></ul></ul><ul><ul><li>Responsible for determining the form and pattern of the ridges on the surface of the skin </li></ul></ul>

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Principal Two <ul><li>Dermal papillae develop in the human fetus </li></ul><ul><li>Ridge patterns will remain unchanged throughout life </li></ul><ul><li>Enlarge during growth </li></ul><ul><li>Fingerprint remains unchanged during lifetime </li></ul>

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Principle Two <ul><li>Skin ridge is populated with pores leading to sweat glands </li></ul><ul><li>Perspiration is deposited on the skin </li></ul>FINGERPRINTS

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Principle Three - Loops <ul><li>A loop must have one or more ridges entering from one side of the print, recurving, and exiting from the same side. </li></ul><ul><ul><li>If the loop opens toward the little finger, it is called an ulnar loop. </li></ul></ul><ul><ul><li>If the loop opens toward the thumb, it is called a radial loop. </li></ul></ul>

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Whorls <ul><li>Plain whorl and central pocket loop have at least one ridge that makes a complete circuit </li></ul><ul><li>Double loop: two loops combined into one fingerprint </li></ul><ul><li>Accidental </li></ul><ul><ul><li>Two or more patterns </li></ul></ul><ul><ul><li>Or pattern not covered by the other categories </li></ul></ul>FINGERPRINTS

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Plain Whorls <ul><li>More than 1 valid delta </li></ul><ul><li>If you look at image A you should be able to identify the two delta's. If not then look at image B and you will see that they are displayed in the red boxes. </li></ul><ul><li>Whorl: one or more ridges which make complete circuit </li></ul><ul><li>Two delta's </li></ul><ul><ul><li>Between which an imaginary line is drawn </li></ul></ul><ul><ul><li>At least one recurving ridge within the inner pattern area cut or touched. </li></ul></ul>

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Whorls <ul><li>Inner area of the pattern forms circle or oval </li></ul><ul><li>Specific ridges that are making or trying to make the circle </li></ul><ul><ul><li>Imaginary line between the two delta's (the red line in image) </li></ul></ul><ul><ul><li>No lines that form the circle are intersected </li></ul></ul>

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Principle Three - Arches <ul><li>Least common of general patterns </li></ul><ul><ul><li>Plain arches </li></ul></ul><ul><ul><li>Tented arches </li></ul></ul><ul><li>No lines that form the circle are intersected </li></ul>FINGERPRINTS

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Plain Arches <ul><li>Ridges entering from one side of the print </li></ul><ul><li>Rising and falling </li></ul><ul><li>Exiting on the opposite side </li></ul><ul><li>Like a wave </li></ul>

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Tented Arches <ul><li>Sharp upthrust or spike </li></ul><ul><li>The ridges meet at an angle that is less than 90 degrees </li></ul><ul><li>Arches do not have type lines, deltas, or cores </li></ul>FINGERPRINTS

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Primary Classification <ul><li>Based on knowledge of fingerprint pattern classes </li></ul><ul><li>Fingers are paired up </li></ul><ul><ul><li>One finger in the numerator of a fraction </li></ul></ul><ul><ul><li>Other in the denominator </li></ul></ul><ul><li>Presence or absence of the whorl pattern </li></ul><ul><ul><li>Basis for the determination of the primary classification </li></ul></ul>FINGERPRINTS

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Primary Classification <ul><li>Values for all 10 fingers totaled </li></ul><ul><li>1 is added to both the numerator and denominator </li></ul><ul><li>Fraction obtained is primary classification. </li></ul>FINGERPRINTS

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Primary Classification <ul><li>25 percent of the population </li></ul><ul><ul><li>1/1 category </li></ul></ul><ul><ul><li>All fingers loops or arches </li></ul></ul><ul><li>Cannot in itself unequivocally identify an individual </li></ul><ul><li>Provides the fingerprint examiner with a number of candidates </li></ul>

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AFIS <ul><li>AFIS aids in classifying and retrieving fingerprints </li></ul><ul><ul><li>Converts image of a fingerprint into digital minutiae </li></ul></ul><ul><ul><li>Contain data showing ridges at their points of termination (ridge endings) and their branching into two ridges (bifurcations). </li></ul></ul><ul><li>Thousands of comparisons per second </li></ul><ul><li>Produces a list of file prints to be examined by a trained fingerprint expert </li></ul>FINGERPRINTS

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Visible Prints <ul><li>Fingers touch a surface after contact with a colored material such as blood, paint, grease, or ink </li></ul><ul><li>Plastic prints: left on a soft material, such as putty, wax, soap, or dust </li></ul><ul><li>Little problem to the investigator </li></ul><ul><li>Usually distinct and visible to the eye. </li></ul>FINGERPRINTS

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Figure 14–17 Schematic depicting latent-print detection with the aid of a laser. A fingerprint examiner, wearing safety goggles containing optical filters, examines the specimen being exposed to the laser light. The filter absorbs the laser light and permits the wavelengths at which latent-print residues fluoresce to pass through to the eyes of the wearer. Courtesy Federal Bureau of Investigation, Washington, D.C.

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Powders <ul><li>Powders, available in a variety of colors, can be applied with a brush or magnetic wand, and adhere to perspiration and/or body oils of the print. </li></ul>

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Digital Imaging <ul><li>Picture converted into digital computer file </li></ul><ul><li>Help of digital imaging software </li></ul><ul><ul><li>Enhanced for the most accurate and comprehensive analysis </li></ul></ul><ul><li>Compare function </li></ul><ul><ul><li>Two images side by side </li></ul></ul><ul><ul><li>Allows the examiner to chart the common features on both images simultaneously </li></ul></ul>FINGERPRINTS